GOLOMB-RICE/EG coding technique for CABAC in HEVC

ABSTRACT

A system utilizing a high throughput coding mode for CABAC in HEVC is described. The system may include an electronic device configured to obtain a block of data to be encoded using an arithmetic based encoder; to generate a sequence of syntax elements using the obtained block; to compare an Absolute-3 value of the sequence or a parameter associated with the Absolute-3 value to a preset value; and to convert the Absolute-3 value to a codeword using a first code or a second code that is different than the first code, according to a result of the comparison.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation U.S. application Ser. No. 16/522,355,filed Jul. 25, 2019, which is a continuation of U.S. application Ser.No. 15/662,791, filed Jul. 28, 2017, now U.S. Pat. No. 10,412,416, whichis a continuation of U.S. application Ser. No. 14/391,422, filed Oct. 9,2014, now U.S. Pat. No. 9,749,656, which is a 371 of InternationalApplication No. PCT/JP2013/002492, filed on Apr. 11, 2013, which claimsthe benefit of U.S. Provisional Application No. 61/622,990, filed onApr. 11, 2012. The contents of each of these applications areincorporated by reference.

TECHNICAL FIELD

The present disclosure relates generally to electronic devices. Morespecifically, the present disclosure relates to electronic devicesutilizing enhanced Context Adaptive Binary Arithmetic Coding (CABAC) forencoding and/or decoding.

BACKGROUND ART

Many decoders (and encoders) receive (and encoders provide) encoded datafor blocks of an image. Typically, the image is divided into blocks andeach of the blocks is encoded in some manner, such as using a discretecosine transform (DCT), and provided to the decoder. A block may denotea rectangular region in an image and consist of pixels, for example a16.times.16 block is a region 16 pixels in width by 16 pixels in height.The decoder receives the encoded blocks and decodes each of the blocksin some manner, such as using an inverse DCT.

Video coding standards, such as MPEG-4 part 10 (H.264), compress videodata for transmission over a channel with limited bandwidth and/orlimited storage capacity. These video coding standards include multiplecoding stages such as intra prediction, transform from spatial domain tofrequency domain, inverse transform from frequency domain to spatialdomain, quantization, entropy coding, motion estimation, and motioncompensation, in order to more effectively encode and decode frames.

The Joint Collaborative Team on Video Coding (JCT-VC) of theInternational Telecommunication Union Telecommunication StandardizationSector (ITU-T) Study Group 16 (SG16) Working Party 3 (WP3) andInternational Organization for Standardization/InternationalElectrotechnical Commission (ISO/IEC) Joint Technical Committee1/Subcommittee 29/Working Group 11 (JTC1/SC29/WG11) has launched astandardization effort for a video coding standard called the HighEfficiency Video Coding standard (HEVC). Similar to some prior videocoding standards, HEVC uses block-based coding. An example of a knownHEVC encoder is shown in FIG. 1. HEVC decoders are also known.

In HEVC, Context-Adaptive Binary Arithmetic Coding (CABAC) is used tocompress Transformed and Quantized Coefficients (TQCs) without loss. TheTQCs are determined at the encoder by processing image blocks with aforward transform to generate transform coefficients that are thenquantized using an operation that maps multiple transform coefficientvalues to TQCs values. The TQCs values are then communicated to thedecoder as coefficient level values, or level values, and the levelvalue for each coefficient is then mapped to a transform coefficientvalue that is similar, but not necessarily identical, to the transformcoefficient value computed at the encoder. CABAC based encoding and/ordecoding technique is generally context adaptive which refers to (i)adaptively coding symbols based on the values of previous symbolsencoded and/or decoded in the past, and (ii) context, which identifiesthe set of symbols encoded and/or decoded in the past used foradaptation. The past symbols may be located in spatial and/or temporaladjacent blocks. In many cases, the context is based upon symbol valuesof neighboring blocks.

As mentioned above, CABAC may be used to compress TQCs without loss. Byway of background, TQCs may be from different block sizes according totransform sizes (e.g., 4.times.4, 8.times.8, 16.times.16, 32.times.32,16.times.32). Two-dimensional (2D) TQCs may be converted into aone-dimensional (1D) array before entropy coding, for example, CABAC. Inan example, 2D arrayed TQCs in a 4.times.4 block may be arranged asillustrated in Table (1).

TABLE 1 4 0 1 0 3 2 −1 . . . −3 0 . . . . . . 0 . . . . . . . . .

When converting the 2D TQCs into a 1D array, the block may be scanned ina diagonal zig-zag fashion. Continuing with the example, the 2D arrayedTQCs illustrated in Table (1) may be converted into 1D arrayed TQCs [4,0, 3, −3, 2, 1, 0, −1, 0, 0, . . . ] by scanning the first row and firstcolumn, first row and second column, second row and first column, thirdrow and first column, second row and second column, first row and thirdcolumn, first row and fourth column, second row and third column, thirdrow and second column, fourth row and first column and so on.

The 1D array of TQCs is represented by a sequence of Syntax Elements(SEs) in CABAC. An example of the sequence of SEs for the example 1Darray of TQCs is shown in FIG. 2. The SEs represent the followingparameters: Last position X/Y, Significance Map, and the attributesGreater than 1, Greater than 2, Sign Information, and Absolute-3. Thelast position X/Y represents the position (X/Y) of the last non-zerocoefficient in the corresponding block. Significance map represents thesignificance of each coefficient, whether the coefficient level is zero.Greater than 1 indicates whether the coefficient amplitude (absolutecoefficient level) is larger than one for each non-zero coefficient(i.e. with significant flag (map) as 1). Greater than 2 indicateswhether the coefficient amplitude is larger than two for eachcoefficient with amplitude larger than one (i.e. with greater than 1flag as 1).

In CABAC in HEVC, the representative SEs are coded. FIG. 3 shows theCABAC framework used for coding SEs. The CABAC coding technique includescoding symbols using stages. In the first stage, the CABAC uses a“binarizer” to map input symbols to a string of binary symbols, or“bins”. The input symbol may be a non-binary valued symbol that isbinarized or otherwise converted into a string of binary (1 or 0)symbols prior to being coded into bits. The bins can be coded into bitsusing either a “bypass encoding engine” or a “regular encoding engine”.

For the regular encoding engine in CABAC, in the second stage aprobability model is selected. The probability model is used toarithmetic encode one or more bins of the binarized input symbols. Thismodel may be selected from a list of available probability modelsdepending on the context, which is a function of recently encodedsymbols. The probability model stores the probability of a bin being “1”or “0”. In the third stage, an arithmetic encoder encodes each binaccording to the selected probability model. There are two sub-rangesfor each bin, corresponding to a “0” and a “1”. The fourth stageinvolves updating the probability model. The selected probability modelis updated based on the actual encoded bin value (e.g., if the bin valuewas a “1”, the frequency count of the “1” s is increased). The decodingtechnique for CABAC decoding reverses the process.

For the bypass encoding engine in CABAC, the second stage involvesconversion of bins to bits omitting the computationally expensivecontext estimation and probability update stages. The bypass encodingengine assumes an equal probability distribution for the input bins. Thedecoding technique for CABAC decoding reverses the process.

The CABAC encodes the symbols conceptually using two steps. In the firststep, the CABAC performs a binarization of the input symbols to bins. Inthe second step, the CABAC performs a conversion of the bins to bitsusing either the bypass encoding engine or the regular encoding engine.The resulting encoded bit values are provided in the bitstream to adecoder.

The CABAC decodes the symbols conceptually using two steps. In the firststep, the CABAC uses either the bypass decoding engine or the regulardecoding engine to convert the input bits to bin values. In the secondstep, the CABAC performs de-binarization to recover the transmittedsymbol value for the bin values. The recovered symbol may be non-binaryin nature. The recovered symbol value is used in remaining aspects ofthe decoder.

As previously described, the encoding and/or decoding process of theCABAC includes at least two different modes of operation. In a firstmode, the probability model is updated based upon the actual coded binvalue, generally referred to as a “regular coding mode”. The regularcoding mode requires several sequential serial operations together withits associated computational complexity and significant time tocomplete. In a second mode, the probability model is not updated basedupon the actual coded bin value, generally referred to as a “bypasscoding mode”. In the second mode, there is no probability model (otherthan perhaps a fixed probability) for decoding the bins, and accordinglythere is no need to update the probability model.

When utilizing CABAC coding in HEVC, throughput performance can differdepending on different factors such as but not limited to: total numberof bins/pixels, number of bypass bins/pixels, and number of regular (orcontext) coded bins/pixels. Throughput is defined as the amount of TQCsthat can be decoded (or encoded) in a unit of time. Generally speaking,throughput for the case of high bit-rate encoding (low QuantizationParameter (QP) value) is significantly less than throughput in othercases. Therefore, throughput in high bit-rate cases may consume asignificant amount of processing resources and/or may take a significantamount of time to encode/decode. The disclosure that follows solves thisand other problems.

It is also known that CABAC can be used in a lossless coding mode tocompress a residual sample. In one example, a residual sample is a valuecorresponding to a specific location in an image. Typically, a residualsample corresponds to the difference between a value corresponding to aspecific location in an image and a prediction value corresponding tothe same, specific location in an image. Alternatively, a residualsample is a value corresponding to a specific location in an image thathas not been processed with a transformation operation, or atransformation operation that is not typically used to create TQCs. Aresidual sample can be from different block sizes according to itssample size (4.times.4, 8.times.8, 16.times.16, 32.times.32,16.times.32, etc.) A 2D residual sample block is first converted into a1D array before entropy coding, similar to TQC encoding. In an example,2D arrayed residual sample in a 4.times.4 block may be arranged asillustrated in Table (2).

TABLE 2 4 0 1 0 3 2 −1 . . . −3 0 . . . . . . 0 . . . . . . . . .

When converting the 2D residual sample into a 1D array, the block may bescanned in a diagonal zig-zag fashion. Continuing with the example, the2D arrayed residual sample illustrated in Table (2) may be convertedinto 1D arrayed residual sample [4, 0, 3, −3, 2, 1, 0, −1, 0, 0, . . . ]by scanning the first row and first column, first row and second column,second row and first column, third row and first column, second row andsecond column, first row and third column, first row and fourth column,second row and third column, third row and second column, fourth row andfirst column and so on.

The 1D array of the residual sample is represented by a sequence ofSyntax Elements (SEs) in CABAC. An example of a sequence of SEs for theexample 1D array of the residual sample is shown in FIG. 2. The SEsrepresent the following parameters: Last position X/Y, Significance Map,and the attributes Greater than 1, Greater than 2, Sign Information, andAbsolute-3.

In the lossless coding mode of CABAC in HEVC, the representative SEs arecoded. The CABAC framework of FIG. 3 may be used for coding the SEs. TheCABAC coding technique includes coding symbols using stages. In thefirst stage, the CABAC uses a “binarizer” to map input symbols to astring of binary symbols, or “bins”. The input symbol may be anon-binary valued symbol that is binarized or otherwise converted into astring of binary (1 or 0) symbols prior to being coded into bits. Thebins can be coded into bits using the previously described “regularencoding engine”.

For the regular encoding engine in the lossless coding mode of CABAC, inthe second stage a probability model (also known as a “context model” inthe lossless encoding mode of CABAC) is selected. The context model isused to arithmetic encode one or more bins of the binarized inputsymbols. This context model may be selected from a list of availablecontext models depending on the context, which is a function of recentlyencoded symbols. The context model stores the probability of a bin being“1” or “0”. In the third stage, an arithmetic encoder encodes each binaccording to the selected context model. There are two sub-ranges foreach bin, corresponding to a “0” and a “1”. The fourth stage involvesupdating the corresponding context model. The selected context model isupdated based on the actual encoded bin value (e.g., if the bin valuewas a “1”, the frequency count of the “1” s is increased). The decodingtechnique for CABAC decoding reverses the process.

The number of context models used as described in the previous paragraphmay be 184. Specifically: 36 context models used for Last position X/Y(18 context models for Last_position_X, 18 context models forLast_position_Y); 48 context models used for Significance Map (4.times.4block: 9 luma, 6 chroma; 8.times.8 block: 11 luma, 11 chroma;16.times.16 or 32.times.32 block: 7 luma, 4 chroma); and 100 contextmodels used for the attributes Greater than 1, Greater than 2, SignInformation, and Absolute-3 (Greater_than.sub.--1 flag of luma: 30;Greater_than.sub.--1 flag of chroma: 20, Greater_than.sub.--2 flag ofluma: 30; and Greater_than.sub.--2 flag of chroma: 20).

(Coding Absolute-3 Coefficients of the Syntax Element)

Referring back to syntax element coding, a portion of the syntax elementcoding involves coding the Absolute-3 coefficients of the syntaxelement. Coding the Absolute-3 coefficients involves Golomb-Rice (GR)coding and 0.sup.th order Exponential-Golomb (EG0) coding, as will beexplained in more detail below.

FIG. 4 illustrates coding structure for Absolute-3 for HEVC.

By way of example, consider the Absolute-3 values shown in FIG. 4,namely, 81, 34, 6, 4, 0. Coding is in reverse relative to scanningorder. The value “0” is converted using the Golomb-Rice (G-R) code tableillustrated in FIG. 5, which shows five Variable-Length Code (VLC)tables (denoted as with the columns labeled 0-4, where column labeled 0is VLC table 0, column labeled 1 is VLC table 1, . . . , column labeled4 is VLC table 4), each corresponding to a different Rice parametervalue. Based on a current Rice parameter of zero (Rice parameter isinitialized at zero for the initial value of a sub-block in HEVC), VLCtable 0 is activated. In the VLC table 0, for the input value of “0”,the codeword is “0”. Therefore, the corresponding codeword value is “0”.

Before proceeding to the next scanning position, there is a check for aRice parameter update. A Rice parameter update table is illustrated inFIG. 6. Because the input symbol level is “0”, and current Riceparameter zero is “0”, a lookup result is zero, the same as the currentRice parameter value, and hence there is no Rice parameter update. ARice parameter update determines the Rice parameter value used to code anext value.

The next value “4” is converted using VLC table 0 of the G-R code tableof FIG. 5 to codeword 11110. According to the update table illustratedin FIG. 6, the current Rice parameter is updated to one beforeconverting the next value “6” to a codeword. Following the conversion ofthe value “6” to a codeword, the Rice parameter is updated to twoaccording to FIG. 6.

Moving to scanning position two, it can be seen that the value “34” toconvert is larger than the Rice code range corresponding to the currentRice parameter two. Specifically, the five Rice parameter values shownin FIG. 5 have, respectively, the following Rice code ranges: 7, 14, 26,46, 78. The range corresponds to the largest symbol value with a definedcodeword and not equal to Ser. No. 11/111,111 for each Rice parameter.Again, the value “34” is larger than the corresponding range 26.Therefore, according to HEVC, a codeword corresponding to the value 27is selected using the VLC table 2 of FIG. 5.

Also, EG0 coding is used to encode the residual value that is notrepresented by the corresponding codeword (11111111 for value 27) fromG-R coding. The input value of the residual, namely 8 (34-26), is usedto select a prefix and suffix from the EG0 table of FIG. 7. Here, theselected prefix from the EG0 process is 1110 and the selected suffixfrom the EG0 process is 001. The Rice parameter is updated to four basedon the value 26 (4 is the lookup result for the largest value 23) andaccording to FIG. 6. Both the codeword 11111111 (from G-R coding) andthe codeword 1110001 (from EG0 coding) are used to represent the value“34”. In an example, the codeword from G-R coding and the codeword fromEG0 coding are concatenated to form a single codeword.

When utilizing CABAC coding in HEVC, throughput performance can differdepending on different factors such as but not limited to the magnitudeof the Absolute-3 values of a syntax element to be coded. Therefore,depending on these factors, coding may consume a significant amount ofprocessing resources and/or may take a significant amount of time. Thedisclosure that follows solves this and other problems.

SUMMARY OF INVENTION

One embodiment of the present invention discloses a method for decodinga bitstream associated with transform coefficients comprising the stepsof: (a) obtaining a bitstream; (b) decoding binary data associated withtarget transform coefficient from the obtained bitstream by using anarithmetic decoding; (c) deriving a rice parameter for said targettransform coefficient; and (d) converting said binary data to aparameter associated with magnitude of said target transform coefficientbased on k-th order Exp-Golomb coding.

Another embodiment of the present invention discloses a method forencoding data associated with transform coefficients comprising thesteps of: (a) obtaining data of target transform coefficient to beencoded using an arithmetic encoding; (b) generating a parameterassociated with magnitude of target transform coefficient using theobtained data; (c) deriving a rice parameter for said target transformcoefficient; (d) converting said parameter to binary data associatedwith magnitude of said target transform coefficient based on k-th orderExp-Golomb coding; and (e) encoding said binary data using saidarithmetic encoding.

Another embodiment of the present invention discloses a system,comprising: an electronic device of an encoder, the electronic deviceconfigured to: obtain a block of data to be encoded using an arithmeticbased encoder; generate a sequence of syntax elements using the obtainedblock; compare an Absolute-3 value of the sequence or a parameterassociated with the Absolute-3 value to a preset value; convert theAbsolute-3 value to a codeword using a first code or a second code thatis different than the first code, according to a result of thecomparison; and cause the codeword to be stored in a memory device.

Another embodiment of the present invention discloses a system,comprising: a electronic device of an encoder, the electronic deviceconfigured to: obtain a block of data to be encoded using an arithmeticbased encoder; generate a sequence of syntax elements using the obtainedblock; determine whether a preset condition associated with the blocksize is met; in response to determining that the preset conditionassociated with the block size is not met, code a binarization of ahorizontal last position based on a first subset of context models andcode a binarization of a vertical last position based on a second subsetof context models that is different than the first subset of contextmodels; in response to determining that the preset condition associatedwith the block size is met, code the binarization of the horizontal lastposition based on the first subset of context models and code thebinarization of the vertical last position based on the first subset ofcontext models; and cause the coding to be stored in a memory device.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a block diagram of an HEVC encoder.

FIG. 2 is a table showing a sequence of syntax elements according toCABAC.

FIG. 3 is a block diagram of the CABAC framework for a sequence ofsyntax elements.

FIG. 4 illustrates coding structure for Absolute-3 for HEVC.

FIG. 5 illustrates a Golomb-Rice code table for HEVC.

FIG. 6 illustrates a Rice Parameter update table for HEVC.

FIG. 7 illustrates an EG0 (0th order Exponential-Golomb) table for HEVC.

FIG. 8 is a block diagram illustrating an example of an encoder and adecoder.

FIG. 9 is a flow diagram illustrating one configuration of a method forcoding using a first Golomb-Rice and/or EG (Exponential-Golomb) codingbased technique on an electronic device.

FIG. 10 illustrates an example of a truncated EG0 table.

FIG. 11 is a flow diagram illustrating one configuration of a method forcoding using the first Golomb-Rice and/or EG coding based technique onan electronic device at the decode-side.

FIG. 12 is a flow diagram illustrating one configuration of a method forcoding using a second Golomb-Rice and/or EG coding based technique on anelectronic device.

FIG. 13 is a flow diagram illustrating one configuration of a method forcoding using the second Golomb-Rice and/or EG coding based technique onan electronic device at the decode-side.

FIG. 14 is a flow diagram illustrating one configuration of a method forcoding using a third Golomb-Rice and/or EG coding based technique on anelectronic device.

FIG. 15 is a flow diagram illustrating one configuration of a method forcoding using the third Golomb-Rice and/or EG coding based technique onan electronic device at the decode-side.

FIG. 16 illustrates context models associated with luma for lastposition coding in known CABAC.

FIG. 17 is a flow diagram illustrating one configuration of a method forshared context modeling for last position coding on an electronicdevice.

FIG. 18 illustrates coding tables that may be utilized in an exampleutilizing the configuration described in FIG. 17.

FIG. 19 is a flow diagram illustrating another configuration of a methodfor shared context modeling for last position coding on an electronicdevice.

FIG. 20 illustrates coding tables that may be utilized in an exampleutilizing the configuration described in FIG. 19.

FIG. 21 is a flow diagram illustrating one configuration of a method forshared context modeling for last position coding on an electronic deviceat the decode-side.

DESCRIPTION OF EMBODIMENTS

FIG. 8 is a block diagram illustrating an example of an encoder and adecoder.

The system 800 includes an encoder 811 to generate encoded blocks to bedecoded by a decoder 812. The encoder 811 and the decoder 812 maycommunicate over a network.

The encoder 811 includes an electronic device 821 configured to encodeusing a Golomb-Rice and/or EG coding based technique. The electronicdevice 821 may comprise a processor and memory in electroniccommunication with the processor, where the memory stores instructionsbeing executable by the processor to perform the operations shown inFIGS. 9, 12, and 14.

The decoder 812 includes an electronic device 822 configured to decodeusing a Golomb-Rice and/or EG coding based technique. The electronicdevice 822 may comprise a processor and memory in electroniccommunication with the processor, where the memory stores instructionsbeing executable to perform the operations shown in FIGS. 11, 13, and15.

FIG. 9 is a flow diagram illustrating one configuration of a method forcoding using a first Golomb-Rice and/or EG coding based technique on anelectronic device.

In block 911, the electronic device 821 obtains a block of transformedand quantized coefficients (TQCs). In block 912, the electronic device821 generates a sequence of syntax elements using the obtained block.

In diamond 913, the electronic device 821 determines whether a magnitudeof an Absolute-3 value is greater than a threshold. If the magnitude isnot greater than the threshold in diamond 913, then in block 914 theelectronic device 821 converts any residual value that is notrepresented by G-R coding of the Absolute-3 value to a codeword using afirst code. In an example, the first code comprises EG0 code.

If the magnitude is greater than the threshold in diamond 913, then inblock 915 the electronic device 821 converts any residual value that isnot represented by G-R coding of the Absolute-3 value to a codewordusing a second code that is different than the first code. In anexample, the second code comprises a truncated EG0 code.

In an example, if the second code is used, the electronic device 821 mayset a high throughput mode indicator, e.g. an HT flag, to a value of 1(which of course may include changing a default value of the HT flag orleaving the HT flag at a default value depending on design preference).

The electronic device 821 transmits the generated bitstream over anetwork and/or stores the generated bitstream in a memory device inblock 916.

An example of a truncated EG0 code is shown in FIG. 10. In the exampleof FIG. 10, the EG0 code is truncated when the input value is greaterthan 254. The longest codeword length using the truncated EG0 table is24 bits, which is shorter than the longest codeword length using an EG0table (29 bits). The suffix showing 15 “x” indications can specify anyvalue in the range of 255 to 33022. For example, suffix value000000000000000 indicates 255, suffix value 000000000000001 indicates256, and so on, with suffix value 111111111111111 indicating 33022.

FIG. 11 is a flow diagram illustrating one configuration of a method forcoding using the first Golomb-Rice and/or EG coding based technique onan electronic device at the decode-side.

In block 1110, the electronic device 822 obtains a bitstream. In block1111, the electronic device 822 obtains a codeword from the obtainedbitstream.

In diamond 1112, the electronic device 822 determines whether a highthroughput decode mode condition is met. In an example, thedetermination may include checking a header, such as a slice header,corresponding to the received bitstream. Checking the header may furthercomprise checking a slice header corresponding to the obtained bitstream for a value of a high throughput decode mode indicator. If thecondition is not met in diamond 1112, then in block 1113 the electronicdevice 822 recovers an Absolute-3 value by applying a first code, e.g.EG0 code, to the codeword.

If the condition is met in diamond 1112, then in block 1114 theelectronic device 822 recovers an Absolute-3 value by applying a secondcode that is different than the first code, e.g. a truncated EG0 code,to the codeword. The electronic device 822 may store an obtained blockof TQCs in a memory device and/or may recover video data in block 1115.

In an example, G-R coding is bypassed for each Absolute-3 value having acorresponding current Rice parameter equal to 4. In an example, EG4 (4thorder) coding is used for the Absolute-3 values that are not processedusing G-R coding. The G-R code table corresponding to Rice parameter 4may not be stored in an example, reducing the memory footprint for G-Rcode tables from 181 bytes to 101 bytes.

FIG. 12 is a flow diagram illustrating one configuration of a method forcoding using a second Golomb-Rice and/or EG coding based technique on anelectronic device.

In block 1211, the electronic device 821 obtains a block of transformedand quantized coefficients (TQCs). In block 1212, the electronic device821 generates a sequence of syntax elements using the obtained block.

In diamond 1213, the electronic device 821 determines whether a currentRice parameter corresponding to an Absolute-3 value is equal to a presetvalue. If the current Rice parameter does not correspond to the presetvalue in diamond 1213, then in block 1214 the electronic device 821converts the Absolute-3 value to a codeword using G-R coding. In block1215, the electronic device 821 uses a first code to code any remainderassociated with the G-R coding.

If the current Rice parameter does correspond to the preset value indiamond 1213, then in block 1216 the electronic device 821 bypasses G-Rcoding for the Absolute-3 value and converts the Absolute-3 value to acodeword using a second code, wherein the second code is different thanthe first code. The electronic device 821 transmits the generatedbitstream over a network and/or stores the generated bitstream in amemory device in block 1217.

In an example, if the second code is used, the electronic device 821 mayset a high throughput mode indicator, e.g. an HT flag, to a value of 1(which of course may include changing a default value of the HT flag orleaving the HT flag at a default value depending on design preference).

FIG. 13 is a flow diagram illustrating one configuration of a method forcoding using the second Golomb-Rice and/or EG coding based technique onan electronic device at the decode-side.

In block 1310, the electronic device 822 obtains a bitstream. In block1311, the electronic device 822 obtains a codeword from the obtainedbitstream.

In diamond 1312, the electronic device 822 determines whether a highthroughput decode mode condition is met. In an example, thedetermination may include checking a header, such as a slice header,corresponding to the received bitstream. Checking the header may furthercomprise checking a slice header corresponding to the obtained bitstream for a value of a high throughput decode mode indicator. If thecondition is not met in diamond 1312, then in block 1313 the electronicdevice 822 recovers an Absolute-3 value by applying G-R coding andconditionally applying a first code, e.g. EG0 code, to the codeword.

If the condition is met in diamond 1312, then in block 1314 theelectronic device 822 recovers an Absolute-3 value by bypassing G-Rcoding and applying a second code that is different than the first codeto the codeword. The electronic device 822 may store an obtained blockof TQCs in a memory device and/or may recover video data in block 1315.In an example, EGk coding is adaptively employed for an Absolute-3 valueaccording to a corresponding current Rice parameter for that Absolute-3value. In an example, EG0 is employed for Absolute-3 values having acorresponding current Rice parameter equal to zero or one. EG1 isemployed for Absolute-3 values having a corresponding current Riceparameter equal to 2 or 3. EG2 is employed for Absolute-3 values havinga corresponding current Rice parameter equal to 4.

FIG. 14 is a flow diagram illustrating one configuration of a method forcoding using a third Golomb-Rice and/or EG coding based technique on anelectronic device.

In block 1411, the electronic device 821 obtains a block of transformedand quantized coefficients (TQCs). In block 1412, the electronic device821 generates a sequence of syntax elements using the obtained block.

In diamond 1413, the electronic device 821 determines whether a currentRice parameter is equal to a preset value. If the current Rice parameteris not equal to the preset value in diamond 1413, then in block 1414 theelectronic device 821 converts an Absolute-3 value associated with thecurrent Rice parameter to a codeword using G-R coding, and uses a firstcode to encode any remainder associated with G-R coding, wherein thefirst code may comprise EG0.

If the current Rice parameter is equal to the preset value in diamond1413, then in block 1415 the electronic device 821 converts anAbsolute-3 value associated with the current Rice parameter to acodeword using G-R coding, and uses a second code to encode anyremainder associated with the G-R coding, wherein the second code isdifferent than the first code. The electronic device 821 transmits thegenerated bitstream over a network and/or stores the generated bitstreamin a memory device in block 1416.

In an example, if the second code is used, the electronic device 821 mayset a high throughput mode indicator, e.g. an HT flag, to a value of 1(which of course may include changing a default value of the HT flag orleaving the HT flag at a default value depending on design preference).

FIG. 15 is a flow diagram illustrating one configuration of a method forcoding using the third Golomb-Rice and/or EG coding based technique onan electronic device at the decode-side

In block 1510, the electronic device 822 obtains a bitstream. In block1511, the electronic device 822 obtains a codeword from the obtainedbitstream.

In diamond 1512, the electronic device 822 determines whether a highthroughput decode mode condition is met. In an example, thedetermination may include checking a header, such as a slice header,corresponding to the received bitstream. Checking the header may furthercomprise checking a slice header corresponding to the obtained bitstream for a value of a high throughput decode mode indicator. If thecondition is not met in diamond 1512, then in block 1513 the electronicdevice 822 recovers an Absolute-3 value by applying G-R coding andconditionally applying a first code, e.g. EG0 code, to the codeword.

If the condition is met in diamond 1512, then in block 1514 theelectronic device 822 recovers an Absolute-3 value by applying G-Rcoding and conditionally applying a second code that is different thanthe first code to the codeword. The electronic device 822 may store anobtained block of TQCs in a memory device and/or may recover video datain block 1515.

(Shared Context Modeling for Last Position Coding for CABAC in HEVC)

By way of background, known CABAC based encoding may utilize contextmodels for arithmetic coding. For coding last position information,known CABAC utilizes thirty context models for luma. These thirtycontext models, namely 0.sub.1-14.sub.1 and 0.sub.2-14.sub.2, are shownin FIG. 16. TU4, TU8, TU16 and TU32 indicate 4.times.4, 8.times.8,16.times.16 and 32.times.32 transform. The context models0.sub.1-14.sub.1 are used to code Pos_X information of the last positioninformation for luma, while the context models 0.sub.2-14.sub.2 are usedto code Pos_Y information of the last position information for luma. Thecontext model selection table 1610 is used for Pos_X, while the contextmodel selection table 1611 is used for Pos_Y.

FIG. 17 is a flow diagram illustrating one configuration of a method forshared context modeling for last position coding on an electronicdevice.

In block 1711, the electronic device 821 obtains a block of transformedand quantized coefficients (TQCs). In block 1712, the electronic device821 generates a sequence of syntax elements using the obtained block.

In diamond 1713, the electronic device 821 determines whether a blocksize is greater than a preset threshold. In an example, the electronicdevice 821 determines whether vertical block size is greater than thepreset threshold. If the block size is not greater than the presetthreshold in diamond 1713, then in block 1714 the electronic device 821codes a binarization of the horizontal last position (Pos_X) based on afirst subset of context models and codes a binarization of the verticallast position (Pos_Y) based on a second different subset of contextmodels that is different than the first subset of context models.

If block size is greater than the preset threshold in diamond 1713, thenin block 1715 the electronic device 821 codes a binarization of thehorizontal last position based on the first subset of context models andcodes a binarization of the vertical last position based on the firstsubset of context models.

In an example, if the coding of the binarization of the vertical lastposition is based on the first subset of context models, the electronicdevice 821 may set a shared context model mode indicator, e.g. an sharedcontext model mode flag, to a value of 1 (which of course may includechanging a default value of the shared context model mode flag orleaving the shared context model mode flag at a default value dependingon design preference).

The electronic device 821 transmits the generated bitstream over anetwork and/or stores the generated bitstream in a memory device inblock 1716.

FIG. 18 illustrates coding tables that may be utilized in an exampleutilizing the configuration described in FIG. 17.

The context model selection table 1810 is used for Pos_X, while thecontext model selection table 1811 is used for Pos_Y. In the exampleillustrated by the tables 1810 and 1811, the preset threshold is 8. Inthe example of FIG. 18, there are twenty one context models, instead ofthirty context models (fifteen context models for Pos_X and six contextmodels for Pos_Y).

FIG. 19 is a flow diagram illustrating another configuration of a methodfor shared context modeling for last position coding on an electronicdevice.

In block 1911, the electronic device 821 obtains a block of transformedand quantized coefficients (TQCs). In block 1912, the electronic device821 generates a sequence of syntax elements using the obtained block.

In diamond 1913, the electronic device 821 determines whether blockwidth and block height are equal. If the block width and block heightare not equal in diamond 1913, then in block 1914 the electronic device821 codes a binarization of the horizontal last position (Pos_X) basedon a first subset of context models and codes a binarization of thevertical last position (Pos_Y) based on a second different subset ofcontext models that is different than the first subset of contextmodels.

If block width and block height are equal in diamond 1913, then in block1915 the electronic device 821 codes a binarization of the horizontallast position based on the first subset of context models and codes abinarization of the vertical last position based on the first subset ofcontext models.

In an example, if the coding of the binarization of the vertical lastposition is based on the first subset of context models, the electronicdevice 821 may set a shared context model mode indicator, e.g. an sharedcontext model mode flag, to a value of 1 (which of course may includechanging a default value of the shared context model mode flag orleaving the shared context model mode flag at a default value dependingon design preference).

The electronic device 821 transmits the generated bitstream over anetwork and/or stores the generated bitstream in a memory device inblock 1916.

FIG. 20 illustrates coding tables that may be utilized in an exampleutilizing the configuration described in FIG. 19.

The context model selection table 2010 is used for Pos_X when blockwidth and block height are equal, while the context model selectiontable 2011 is used for Pos_Y when block width and block height areequal. In an example, the context model selection tables 1610 and 1611(FIG. 16) may be used when block width and block height are not equal.

FIG. 21 is a flow diagram illustrating one configuration of a method forshared context modeling for last position coding on an electronic deviceat the decode-side.

In block 2110, the electronic device 822 obtains a bitstream. In block2111, the electronic device 822 obtains a codeword from the obtainedbitstream.

In diamond 2112, the electronic device 822 determines whether a presetcondition associated with block size is met. In an example, thedetermination may include checking a header, such as a slice header,corresponding to the received bitstream. Checking the header may furthercomprise checking a slice header corresponding to the obtained bitstream for a value of a shared context model mode indicator. If thepreset condition is not met in diamond 2112, then in block 2113 theelectronic device 822 recovers a horizontal last position value based ona first subset of context models and recovers a vertical last positionvalue based on a second subset of context models that is different thanthe first subset of context models.

If the preset condition is met in diamond 2112, then in block 2114 theelectronic device 822 recovers a horizontal last position value based ona first subset of context models and recovers a vertical last positionvalue based on the first subset of context models. The electronic device822 may store an obtained block of TQCs in a memory device and/or mayrecover video data in block 2115.

The system and apparatus described above may use dedicated processorsystems, micro controllers, programmable logic devices, microprocessors,or any combination thereof, to perform some or all of the operationsdescribed herein. Some of the operations described above may beimplemented in software and other operations may be implemented inhardware. One or more of the operations, processes, and/or methodsdescribed herein may be performed by an apparatus, a device, and/or asystem substantially similar to those as described herein and withreference to the illustrated figures.

A processing device may execute instructions or “code” stored in memory.The memory may store data as well. The processing device may include,but may not be limited to, an analog processor, a digital processor, amicroprocessor, a multi-core processor, a processor array, a networkprocessor, or the like. The processing device may be part of anintegrated control system or system manager, or may be provided as aportable electronic device configured to interface with a networkedsystem either locally or remotely via wireless transmission.

The processor memory may be integrated together with the processingdevice, for example RAM or FLASH memory disposed within an integratedcircuit microprocessor or the like. In other examples, the memory maycomprise an independent device, such as an external disk drive, astorage array, a portable FLASH key fob, or the like. The memory andprocessing device may be operatively coupled together, or incommunication with each other, for example by an I/O port, a networkconnection, or the like, and the processing device may read a filestored on the memory. Associated memory may be “read only” by design(ROM) by virtue of permission settings, or not. Other examples of memorymay include, but may not be limited to, WORM, EPROM, EEPROM, FLASH, orthe like, which may be implemented in solid state semiconductor devices.Other memories may comprise moving parts, such as a conventionalrotating disk drive. All such memories may be “machine-readable” and maybe readable by a processing device.

Operating instructions or commands may be implemented or embodied intangible forms of stored computer software (also known as “computerprogram” or “code”). Programs, or code, may be stored in a digitalmemory and may be read by the processing device. “Computer-readablestorage medium” (or alternatively, “machine-readable storage medium”)may include all of the foregoing types of memory, as well as newtechnologies of the future, as long as the memory may be capable ofstoring digital information in the nature of a computer program or otherdata, at least temporarily, and as long as the stored information may be“read” by an appropriate processing device. The term “computer-readable”may not be limited to the historical usage of “computer” to imply acomplete mainframe, mini-computer, desktop or even laptop computer.Rather, “computer-readable” may comprise storage medium that may bereadable by a processor, a processing device, or any computing system.Such media may be any available media that may be locally and/orremotely accessible by a computer or a processor, and may includevolatile and non-volatile media, and removable and non-removable media,or any combination thereof.

A program stored in a computer-readable storage medium may comprise acomputer program product. For example, a storage medium may be used as aconvenient means to store or transport a computer program. For the sakeof convenience, the operations may be described as variousinterconnected or coupled functional blocks or diagrams. However, theremay be cases where these functional blocks or diagrams may beequivalently aggregated into a single logic device, program or operationwith unclear boundaries.

One of skill in the art will recognize that the concepts taught hereincan be tailored to a particular application in many other ways. Inparticular, those skilled in the art will recognize that the illustratedexamples are but one of many alternative implementations that willbecome apparent upon reading this disclosure.

Although the specification may refer to “an”, “one”, “another”, or“some” example(s) in several locations, this does not necessarily meanthat each such reference is to the same example(s), or that the featureonly applies to a single example.

What is claimed is:
 1. A method for encoding transform coefficientsrepresenting a block of an image, comprising: obtaining data associatedwith a target transform coefficient to be encoded; generating aplurality of flags indicating whether the target transform coefficientis greater than a particular value; deriving a difference between thetarget transform coefficient and the particular value; deriving a Riceparameter for the target transform coefficient; generating binary dataassociated with magnitude of the difference between the target transformcoefficient and the particular value based on a combination of a Ricecode corresponding to the Rice parameter and a first or a second codewherein the first code is a k-th order exponential Golomb code; andgenerating, based on the binary data, a bitstream representing a codedimage, the bitstream comprising: (i) a first syntax element, wherein acombination of the plurality of flags and the first syntax elementindicates the magnitude of the transform coefficient, and (ii) anindicator indicative of whether the first or the second code is used incombination with the Rice code, wherein the indicator is a flag that isdifferent from the Rice parameter.
 2. The method of claim 1, wherein thevalue k of the k-th order exponential Golomb code is determined based onthe Rice parameter.
 3. The method of claim 1, wherein generating thebitstream comprises encoding the binary data using arithmetic encoding.4. The method of claim 1, wherein generating the binary data comprises:generating, from the obtained data, a second parameter, different fromthe Rice parameter, the second parameter being associated with themagnitude of the target transform coefficient.
 5. The method of claim 4,further comprising converting the second parameter to the binary databased on the combination of (i) the Rice code and (ii) the first or thesecond code.